An Empirical Study of Gunpowder Residue Patterns

The muzzle-to-target distance is often a factor of critical importance in incidents involving gunshot wounds. The degree of concern is dependent on the wound severity and the facts of the event, those facts being of greatest moment in a possible homicide/suicide without witnesses and diminishing in importance in a nonfatal accidental shooting with witnesses. The testimony of an expert witness will attempt, through his experimentation, to establish the minimum distance from muzzle to projectile contact point based on the presence or absence of powder residue patterns on the victim or his garments. It should be understood that in casework, the powder residue examined by the laboratory is seldom the total pattern originally blown into the skin or clothing of the victim, but rather that surviving the victim's fall, first aid ministrations, the physician's examination, and, finally, the investigative and packaging efforts of law enforcement. In some instances, portions of the latent elements can be reconstructed by chemical or infrared techniques. To avoid errors of interpretation the investigator must be aware of the variations in pattern imprints, the causative factors, and their significance as related to distance.